ISARIC identifies four COVID-19 risk groups

Doctors treating hospitalised patients

People admitted to hospital with COVID-19 can be divided into four distinct groups, according to data from the world’s largest study of patients with the disease.

Researchers used clinical information and tests carried out on arrival at hospital to predict the patients’ risk of death – ranging from low to very high.

The COVID-19 risk identification tool will help clinical staff choose the best course of treatment for patients admitted to hospital.

It was built by the ISARIC Coronavirus Clinical Characterisation Consortium, involving researchers from the universities of Edinburgh, Glasgow and Liverpool, and Imperial College London.

The project was funded by UKRI and by the Department of Health and Social Care through the National Institute for Health Research, as part of the UK government’s COVID-19 rapid research response.

Predicting risk

The ISARIC researchers used data from 35,000 patients admitted to hospital between February and May 2020 who met the criteria for one of the four groups.

The tool was tested and its accuracy confirmed using data from a further 22,000 patients hospitalised from the end of May to the end of June 2020.

Some of the data used to identify which group a person falls into – and therefore their risk of dying – included age, sex, the number of pre-existing conditions, respiratory rate on admission and the results of two blood tests.

One in every 100 patients in the low-risk group was found to be at risk of dying.

That number was 10 in 100 patients in the intermediate-risk group, 31 in 100 in the high-risk group and 62 in 100 in the very high-risk group.

The first accurate risk tool for COVID-19

The categorisations make new treatment pathways possible, the researchers say.

People who fall into low-risk subgroups could be treated at home, while those in the high or very high-risk groups could have more aggressive treatment like early admission to critical care.

This is the first accurate risk tool for COVID-19 patients. Existing tools for pneumonia or sepsis do not offer accurate predictions due to the differences between diseases.

One limitation of this new tool is that it can only be used on hospital patients, and not within the community.

Pandemic preparedness

Professor Fiona Watt, Executive Chair of the Medical Research Council (MRC) said:

These results highlight the benefits of being prepared in advance of the emergence of new pandemics such as COVID-19.

The work is the latest result from ISARIC – a global network of clinicians and scientists who have been preparing to prevent disease and death from severe outbreaks since 2012 in readiness for a pandemic such as this.

It involved 260 hospitals across England, Wales and Scotland.

The ISARIC 4C study includes two thirds of all people admitted to hospital with COVID-19.

See the published findings in the British Medical Journal (BMJ).

Women under 50 have worse long-term outcomes

ISARIC’s data continues to shed light on who is worst-affected by COVID-19.

In early 2021, a new study showed women under 50 and those who had experienced severe disease had worse long-term outcomes.

Female participants under the age of 50 years old were:

  • five times less likely to report feeling fully recovered
  • twice as likely to report worse fatigue
  • seven times more likely to be more breathless and were
  • more likely to have worsening difficulties or a new disabilities, especially relating to:
    • memory
    • mobility
    • communication
    • vision
    • hearing
    • self-care.

Dr Janet Scott, from the University of Glasgow MRC Centre for Virus Research, lead author of the study, said:

The fact that women under the age of 50 are the group with the worst outcomes could have profound implications for pandemic policy decisions, as well as vaccination strategy.

Additional information

ISARIC is a federation of 55 research networks spanning 111 countries. The networks generate the evidence for improving clinical care and responses to infectious disease epidemics. They also support the development and evaluation of new diagnostics, treatments and vaccines.

In 2009, outbreaks like the H1N1 swine flu pandemic showed that cross-border coordination is vital to improve clinical and public health responses to rapidly-emerging infectious diseases.

The MRC provided initial seed funding to establish ISARIC, and in 2011 it gained funding from:

  • MRC
  • Institut National de la Santé et de la Recherche Médicale (INSERM)
  • the Bill and Melinda Gates Foundation
  • the Wellcome Trust.

ISARIC’s protocols and infrastructure have been instrumental in the global response to COVID-19. The RECOVERY trial is just one example.

Last updated: 14 May 2021

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